X-Plus has now revealed their Large Monster Series Sanda Vs. Gaira Ric exclusive set that was teased a few days ago. This set includes both monsters, a second set of arms for each, a base, and a moving eye gimmicks. Sanda stands 24cm tall (slightly under 9.5 inches), Gaira 22cm tall (slightly over 8.5 inches), and the set retails for 27,000 yen (approx $251 US). They can be pre-ordered from the X-Plus site now with release scheduled for April 2018.
Update: The standard versions are now up on sites like AmiAmi and Hobby Search, they are individual figures without the base, extra arms, or movable eyes. These figures come with the arms posed for separate display (not the "fighting" arms), each figure will retail for 12,960 yen (approx $121 US). Also a new pic has been added showing the movable eyes (bottom).